The overall objective of this research project is to study the regulation of serum protein synthesis in cultured mouse hepatoma cells (Hepa). The experimental situations to be investigated are designed to simulate physiologic changes believed to regulate serum protein synthesis in the liver. Additionally, studies of the effects of specific antibodies on antigen synthesis will be conducted. The objective of these latter experiments is to understand the role of antibodies in the development of hepatocarcinoma. The cell line (Hepa) to be used in these investigations was derived from the mouse hepatoma BW7756 (Jackson Laboratory). These cells secrete albumin, alpha-fetoprotein and transferrin into the culture medium. The rates at which the proteins are synthesized and secreted depend upon growth conditions. The following regulatory phenomena will be studied in Hepa: 1) autoregulation of albumin synthesis, 2) effects of essential amino acids on albumin synthesis, 3) effects of cyclic AMP on serum protein synthesis, and 4) the effects of antibodies to specific proteins on the synthesis of their antigens. The experimental parameters to be evaluated are 1) cellular rate of synthesis (molecules/cell/minute), 2) polyribosome size, and 3) translation rate (polypeptides/minute). These measurements will allow the calculation of two additional protein synthetic parameters: 1) the rate of ribosome initiation on specific mRNAs and 2) the number of functional mRNA molecules per cell.